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From:   Jiri Olsa <olsajiri@gmail.com>
Date:   Mon, 24 Jul 2023 10:18:48 +0200
To:     Baoquan He <bhe@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>,
        Jiri Olsa <olsajiri@gmail.com>,
        Lorenzo Stoakes <lstoakes@gmail.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Uladzislau Rezki <urezki@gmail.com>,
        Matthew Wilcox <willy@infradead.org>,
        Liu Shixin <liushixin2@huawei.com>,
        Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v8 1/4] fs/proc/kcore: avoid bounce buffer for ktext data
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On Mon, Jul 24, 2023 at 04:08:41PM +0800, Baoquan He wrote:
> On 07/24/23 at 08:23am, David Hildenbrand wrote:
> > Hi,
> > 
> > > 
> > > I met this too when I executed below command to trigger a kcore reading.
> > > I wanted to do a simple testing during system running and got this.
> > > 
> > >    makedumpfile --mem-usage /proc/kcore
> > > 
> > > Later I tried your above objdump testing, it corrupted system too.
> > > 
> > 
> > What do you mean with "corrupted system too" --  did it not only fail to
> > dump the system, but also actually harmed the system?
> 
> From my testing, reading kcore will cause system panic, then reboot. Not
> sure if Jiri saw the same phenomenon.

it did not crash for me, just the read error
could you get console output from that?

jirka

> 
> > 
> > @Lorenzo do you plan on reproduce + fix, or should we consider reverting
> > that change?
> 
> When tested on a arm64 system, the reproducution is stable. I will have
> a look too to see if I have some finding this week.
>